A common occurrence during semiconductor device fabrication is the accumulation of particulate contaminants on semiconductor device surfaces. Various processes and cleaning solutions have been used for the removal of small residual particles and other contaminants from surfaces, such as a wafer surface in the fabrication of semiconductor-based structures and devices. A post-process clean is typically conducted to remove contaminants remaining on a surface after a processing step such as etching, planarization, polishing, sawing, film deposition, etc., prior to performing another device fabrication step such as a metallization, gate or device formation, etc. If residues or contaminants remaining from a process step are not effectively removed, various fabrication problems and defects in the finished integrated circuit device can result. For example, metal contaminants that remain on a surface feature can cause shorts between capacitor electrodes or other electrical failures, and non-conductive contaminants on a feature such as particles (e.g., SiO2, polysilicon, nitride, polymers, etc.) remaining after a chemical-mechanical planarization or polishing (CMP) or other process can cause the failure in adhesion of subsequent layers, a loss of critical dimension of the formed feature, or pattern deformation in that area leading to yield loss. Current technology nodes (e.g., 65 nm and smaller) require a high level of surface cleaning, including the removal of remnant particles, residues and other contaminants while maintaining other surface materials intact.
One example of a known cleaning technique used to remove unwanted surface materials is an RCA clean, which conventionally includes first applying an aqueous alkaline cleaning solution known as a Standard Clean 1 (SC1) to remove particle contaminants. SC1 typically consists of a dilution of ammonium hydroxide/hydrogen peroxide (NH4OH/H2O2) followed by a deionized (DI) water rinse. An example of a cleaning technique to remove metal contaminants is an aqueous acidic cleaning solution known as a Standard Clean 2 (SC2) composed of a hydrochloric acid/hydrogen peroxide (HCl/H2O2) dilution followed by a second DI water rinse. Other wet cleaning methods used for cleaning residues from structures include, for example, a piranha clean using a sulfuric acid-based mixture (e.g., H2SO4/H2O2), a buffered oxide etch solution, and fluorine-based aqueous chemistries.
Small particles or other contaminants resulting from fabrication steps can be held to a surface by electrostatic and/or other forces and can become adhered, typically requiring relatively large forces to remove them. Cleaning solutions are often applied in conjunction with acoustic energy (i.e., ultrasonic or megasonic energy), high pressure spraying techniques, mechanical scrubbing techniques with a pad or brush, etc., to enhance the cleaning action of the solution. However, acoustic cleaning and spraying techniques apply cleaning forces in a manner that is difficult to control, which can cause damage to surface structures or alter critical dimensions without effectively removing all of the particulate contaminants from the substrate. In addition, many cleaning solutions can attack and/or dissolve the structures formed in the fabrication step.
Other techniques involve forcing solid particles (e.g., salts of fatty acid solids, paraffin, wax, polymers, etc.) dispersed within a continuous phase to a substrate surface to disengage surface contaminants, which can damage to line elements and other surface structures. For example, some techniques apply a chemical or foam that contains salts of fatty acid solids (e.g., crystals of stearic acid salts) by dispensing from a rotary head or proximity cleaning head. However, stearic acid crystal size and its velocity in a dynamic foam are difficult to control, resulting in damage to surface structures (e.g., line elements) by poorly controlled parameters within the foam.
It would be desirable to provide a process for removing contaminants from a surface without adversely affecting structures and/or surface materials on a substrate that overcomes these problems.